Soils in many parts of the world are susceptible to compaction for various reasons (e.g., high clay content, low organic matter content, poor structure, etc.) and consequently do not exhibit good internal drainage characteristics. Also, such soils have poor macro-porosity. As a result, root development in these types of soils is restricted due to poor oxygen diffusion and mechanical impedance. Similar problems are exhibited by soils in areas where there is a significant amount of traffic (e.g., athletic playing fields such as football and soccer fields; golf courses; pathways; and the like).
Thus, in areas which are subject to traffic or where soils are susceptible to compaction for various reasons it can be very difficult to grow and maintain healthy grass or sod or other plant species. Although there are commercially available techniques for increasing the porosity of soil in which grass is growing, such as cutting and removing small soil plugs from the area, such techniques can be expensive and time consuming. Furthermore, in order to be effective, the soil plug removal technique must involve a significant percentage of the entire area to be effectively aerated. Also, this technique often must be repeated several times each year or so in order to maintain the desired porosity in the soil.
A further disadvantage of the soil plug removal is that the soil plugs are normally left laying on top of the sod. This results in a messy appearance and could interfere with certain sports activities being conducted on the sod. Removal of the soil plugs from the surface of the sod is possible but it is time-consuming and also expensive.
Another type of aeration technique involves the use of an apparatus which simply punches holes in the ground but does not remove a core or plug. Also, there are slicers which have blades or knives to create a slit in the ground. More recently there have been developed shatter-type aerators as well as aerators which extend as deep as nine inches into the ground.
Renovation of turf grass almost always includes a program of aeration. However, benefits from aeration will only be significant when the right equipment is used at the proper time, including the optimum soil moisture level.
The use of sand as a top dressing has been tried in the past. However, in most cases this tends to produce a negative result.
The optimum time to assure maximum porosity is during the period of soil preparation. At this critical time, attention must be paid to the physical and chemical characteristics of the soil and what amendments can be added to enhance soil structure and porosity. Roots grow in spaces between soil particles and in the pores of larger soil aggregates.
Peat moss has also been added to soil. However, this material is becoming more expensive and there is only a relatively short time over which the peat moss is active in the soil.
For farm crops, soil ripping, slit tilling, sub-soiling and other expensive mechanical techniques are used to improve drainage.
If the soil in which grass or sod is growing does not possess proper porosity and drainage characteristics, then root growth of the grass is restricted. In compacted soils the availability of both water and oxygen as well as other nutrients is low. Therefore, grasses on these soils are subject to stress and become more susceptible to disease and insect infestation. Ultimately the grass will die. Then the soil must be ripped or tilled and new sod laid on top of it, or grass seed and fertilizer must be applied in an attempt to grow new sod. This also is a time-consuming and expensive task.
All too often the quick-fix is resorted to in turf grass management problems. Examples of this are the application of fertilizer, fungicides, insecticides, herbicides, and more irrigation water, thereby potentially causing serious ground water pollution problems. The reason for this is that soil compaction is not easily observed and diagnosed.
Another problem with compacted soils in athletic fields is that the ground is much harder than desired and can cause injuries to players. Thus, compacted soils can also be dangerous to players as well as being detrimental to the growing of grass or sod. Also, compacted soils create hazards for athletes, and horses in equestrian events. In addition to the field hardness per se, soil compaction also reduces the shear strength of the turf causing poor footing for the players and the loss of turf (divots).